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Old 02-24-2014, 01:02 PM   #1
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Back spacing for 33/12.5/15 tires

I'm getting ready to get into the wrangler community, so I've started my research on the lift and tires I will be installing. I'm 80% positive I'm going with the Zone 4.25 combo lift. My only issue with that lift is I'm trying to get the tires to stick out an inch or two from the stock fenders. The specs for that lift state that the max tire size for that lift is 33/12.5/15x8 with a 3.5" back spacing.. I know that won't get the tires to stick out. Would a 4-5" backspacing give me the inch or two I'm looking for?

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Old 02-24-2014, 01:15 PM   #2
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If you want the tires to stick out, you want less backspacing, not more. 3.5" will absolutely stick the tires out past the fenders.

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Old 02-24-2014, 01:16 PM   #3
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3.5 is more wheel and tire sticking out from the axle than 4 or 5.
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Old 02-24-2014, 01:35 PM   #4
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for 33x12.50R15, you want 3.75-4.25" backspacing. anything more and you'll rip the tires up on the rear spring perch, anything less and your scrub radius will suck a lot.

you may find wider flares beneficial with the wider tires & backspacing change.
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Old 02-24-2014, 01:42 PM   #5
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If you say less is more, does that also apply to the rim width as well? So would I get more of the tire sticking out if I went with a 15x7 over a 15x8?
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Old 02-24-2014, 05:56 PM   #6
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Quote:
Originally Posted by tim.annoni View Post
If you say less is more, does that also apply to the rim width as well? So would I get more of the tire sticking out if I went with a 15x7 over a 15x8?
Well it is not so much a fact of "less is more" in the case of backspacing. This may not be 100% accurate, but it close enough to give you an idea of what backspacing means: backspacing is a measurement from where the wheel is mounted on the axle to the edge of the wheel on the inner side.

In actuality, 15x8 wheels would cause your tires to stick out more than 15x7 wheels, IF they have the same backspacing. Here is an example to see how this works: let's say they both have 4" backspacing. That means both wheels go 4" inward from where they are mounted. However, this leaves 4" left unaccounted for on the 15x8 and 3" left unaccounted on the 15X7. That means that the 15x8 will stick out 4" from where the wheel is mounted, and the 15x7 will stick out 3" from where the wheel is mounted. In other words, the center of the 15x8 actually 0.5" farther "out" than the 15x7.
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Old 02-24-2014, 06:52 PM   #7
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Quote:
Originally Posted by turnbull View Post
Well it is not so much a fact of "less is more" in the case of backspacing. This may not be 100% accurate, but it close enough to give you an idea of what backspacing means: backspacing is a measurement from where the wheel is mounted on the axle to the edge of the wheel on the inner side. In actuality, 15x8 wheels would cause your tires to stick out more than 15x7 wheels, IF they have the same backspacing. Here is an example to see how this works: let's say they both have 4" backspacing. That means both wheels go 4" inward from where they are mounted. However, this leaves 4" left unaccounted for on the 15x8 and 3" left unaccounted on the 15X7. That means that the 15x8 will stick out 4" from where the wheel is mounted, and the 15x7 will stick out 3" from where the wheel is mounted. In other words, the center of the 15x8 actually 0.5" farther "out" than the 15x7.
From what I've read and heard, this is exactly correct.

Depending on what factory wheels your jeep as now, your back spacing is either 5", 5.5" or 5.25" if you have the "Gambler" wheels. (someone please correct me if I'm wrong) For example, I have the "Ravine" wheels on my 06 which have 5.5 backspacing and I'm playing on getting the pro comp series 51 15x8 with the 3.75 back spacing so once I get them, they will stick out 1.75" further than they do now.

Keep in mind, that scenario doesn't account for wider tires, only a smaller amount of back spacing for the wheels.
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Old 02-24-2014, 07:49 PM   #8
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I am running American Racing Ventura 15x10 wheels and BFG 33x12.5 tires on my 2000TJ with stock fenders.
I would swear the wheels have 3.75 backspacing. The tires stick out a couple inches and look awesome.
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